The present invention relates to a method and apparatus for measuring a shape of bumps formed on a board (a substrate) in manufacturing a multilayer printed board or in mounting a semiconductor device on a board. The present invention further relates to a method for manufacturing the multilayer printed board, including management of the bump shape.
In recent years, a tendency to manufacture a miniaturized multilayer printed board is increasing to realize high accuracy and high density. The interlayer connection in the multilayer printed board is predominantly performed by a method where holes are provided in the connection part using a drill, a laser, or the like to realize electric conduction by plating. However, in recent years, a connection method using bumps is being applied with the tendency of high density and low cost.
On the other hand, a technology for imaging, using a camera, projection like bump electrodes formed on a semiconductor device and the like and for determining the quality of the electrodes by image processing is known in Japanese Patent Laid-open No. 11-26534, FIG. 4 and page 4 (conventional technology 1) and Automation, Vol. 46, No. 4, pages 15 to 18, FIGS. 4 and 5 (April, 2001) (conventional technology 2).
The conventional technology 1 describes the following. Specifically, illumination light composed of light beams traveling parallel to a principal surface of a circuit component or light beams having components parallel to a principal surface of the circuit component is projected onto bump electrodes. Reflected light of the illumination light to a direction perpendicular to the principal surface is incident on an imaging unit. Then, the detected image data obtained from the imaging device are compared with reference image data preliminarily stored in a storage unit to thereby determine the quality of the bump electrodes according to the level of the agreement between both the data.
The conventional technology 2 describes a method for measuring a height of bumps from images, where bumps are irradiated with illumination light from those oblique directions to allow detection of a shadow length of the bumps.
When a connection method of using bumps is employed in order to manufacture the multilayer printed board, the following steps are performed. Specifically, immediately after a step of forming bumps on the lower printed board, a bump shape measuring apparatus is used to check whether shapes such as the position, height and bottom diameter of the bumps are manufactured on the whole board according to the design. Based on the results, the lower printed board and the upper printed board are pressurized to allow conductive connection using the bumps. At this time, the possibility of causing conducting failure must be eliminated in order to secure high yields.
On the other hand, a number of products using such a multilayer printed board, e.g., a cellular phone and a digital camera, need small sized high density mounting. The cost in the printed board itself is reduced due to reduction in the cost of products. Therefore, the bump shape measuring apparatus also is required to be inexpensive and speedy. Further, the apparatus is required to have high measuring accuracy to secure high reliability for the multilayer printed board.
In the conventional technologies 1 and 2, however, adequate consideration is not given to these points.